1. Field of the Invention
The present invention relates to a traction control method for motor vehicles and an apparatus for working such a method, and more particularly it pertains to such method and apparatus wherein a slip of driving wheel which tends to be caused when the motor vehicle starts or accelerates, is detected to control the output of the motor vehicle engine and braking of the driving wheel, thereby restraining the slip of the driving wheel.
2. Description of the Prior Art
Known in the art is a traction control system for motor vehicles, which is arranged, when the motor vehicle runs on a low-friction road surface such as a frozen, snow-covered or muddy one, to restrain a slip of driving wheel which tends to be caused in an attempt to start or accelerate the motor vehicle, thereby enhancing the starting/accelerating performance as well as the running stability of the vehicle. With such a conventional traction control system, it has been the usual practice that a slip of each of the lefthand and righthand driving wheels is detected; and when the extent of the slip exceeds a predetermined value, a brake hydraulic pressure applied to a brake device for each driving wheel is increased so that the braking of the driving wheels is controlled, while at the same time the engine output is also controlled, as disclosed in Japanese Patent Publication (Laid-Open) No. 61-85248.
However, such a conventional traction control system is disadvantageous in that when it is attempted to control the brake hydraulic pressure applied to the brake device for each of the left hand and righthand driving wheels, there is a tendency that the difference between the lefthand and righthand driving wheel speeds is increased so that a hunting phenomenon is caused to occur; and in addition, difficulty is encountered in securing a match between the brake hydraulic pressure control and the engine output control due to the difference in response speed therebetween so that an uncomfortable feeling is given to the driver and a vibration is imparted to the vehicle body.